Preheat your oven to 425°F. Line a large rimmed baking sheet with unbleached parchment paper and set it aside.

In a large bowl, place the flour, xanthan gum, cornstarch, baking powder, baking soda, salt and sugar, and whisk to combine well. Add the diced or grated and chilled butter, and mix to combine.

Create a well in the center of the dry ingredients, add the buttermilk and mix until just combined.

Working quickly, so the dough doesn’t get warm, drop the batter by the quarter cup using two large spoons or a 2-inch ice cream scoop about 1 ½-inches apart on the prepared baking sheet. Do not pack the dough into the ice cream scoop.

Press the mounds of dough down gently to flatten the tops, and brush lightly with the melted butter.

Place the baking sheet in the center of the preheated oven and bake until lightly golden brown all over (about 15 minutes). Remove from the oven and allow to set briefly before serving.